The Liane is a 38 km long river in the
Pas-de-Calais
Pas-de-Calais (, " strait of Calais"; pcd, Pas-Calés; also nl, Nauw van Kales) is a department in northern France named after the French designation of the Strait of Dover, which it borders. It has the most communes of all the departments ...
department in northern
France
France (), officially the French Republic ( ), is a country primarily located in Western Europe. It also comprises of Overseas France, overseas regions and territories in the Americas and the Atlantic Ocean, Atlantic, Pacific Ocean, Pac ...
. It rises in
Quesques and flows into the
English Channel
The English Channel, "The Sleeve"; nrf, la Maunche, "The Sleeve" (Cotentinais) or ( Jèrriais), (Guernésiais), "The Channel"; br, Mor Breizh, "Sea of Brittany"; cy, Môr Udd, "Lord's Sea"; kw, Mor Bretannek, "British Sea"; nl, Het Kana ...
at
Boulogne-sur-Mer
Boulogne-sur-Mer (; pcd, Boulonne-su-Mér; nl, Bonen; la, Gesoriacum or ''Bononia''), often called just Boulogne (, ), is a coastal city in Northern France. It is a sub-prefecture of the department of Pas-de-Calais. Boulogne lies on the ...
. Other communes along its length include:
Selles,
Brunembert,
Bournonville
August Bournonville (21 August 1805 – 30 November 1879) was a Danish ballet master and choreographer. He was the son of Antoine Bournonville, a dancer and choreographer trained under the French choreographer, Jean Georges Noverre, and the ne ...
,
Alincthun,
Crémarest,
Wirwignes,
Questrecques,
Samer
Samer (; pcd, Samé; vls, Sint-Wulmaars) is a commune and in the Pas-de-Calais department in the Hauts-de-France region of France.
Population
Places of interest
* The church of St.Martin, dating from the 15th century.
* The château du Gr ...
,
Carly,
Hesdigneul-lès-Boulogne
Hesdigneul-lès-Boulogne (, literally ''Hesdigneul near Boulogne''; pcd, Hédignu-lès-Boulonne) is a commune in the Pas-de-Calais department in the Hauts-de-France region of France.
Geography
A forestry and farming village situated some so ...
,
Isques
Isques (; nl, Izeke) is a commune in the Pas-de-Calais department in the Hauts-de-France region of France.
Geography
A forestry, farming and dormitory village situated some south of Boulogne, at junction 28 of the A16 autoroute with the D901 ( ...
,
Saint-Léonard,
Hesdin-l'Abbé,
Condette
Condette () is a commune in the Pas-de-Calais department in the Hauts-de-France region of France.
Geography
A large farming, forestry and tourist village, some south of Boulogne-sur-Mer, at the junction of the D240 and the D940 roads. The riv ...
,
Saint-Étienne-au-Mont
Saint-Étienne-au-Mont (; pcd, Sant-Étienne-au-Mont; obsolete nl, Sint-Stevensbergen, ) is a commune in the Pas-de-Calais department in the Hauts-de-France region of France near Boulogne-sur-Mer. Besides the main settlement Saint-Étienne-a ...
, and
Outreau
Outreau (; vls, Wabingen) is a commune in the Pas-de-Calais department in the Hauts-de-France region of France.
Geography
Outreau is a large industrial town and port situated adjacent to, and west of Boulogne, on the N1, N142 and D19 roads. Th ...
.
Geography
The Liane flows for a length of 38.2 km.
It rises at
Quesques, then flows through the communes of
Bournonville
August Bournonville (21 August 1805 – 30 November 1879) was a Danish ballet master and choreographer. He was the son of Antoine Bournonville, a dancer and choreographer trained under the French choreographer, Jean Georges Noverre, and the ne ...
,
Wirwignes,
Questrecques,
Carly,
Hesdigneul,
Isques
Isques (; nl, Izeke) is a commune in the Pas-de-Calais department in the Hauts-de-France region of France.
Geography
A forestry, farming and dormitory village situated some south of Boulogne, at junction 28 of the A16 autoroute with the D901 ( ...
and
Saint-Léonard. It finally flows into the English channel at
Boulogne-sur-Mer
Boulogne-sur-Mer (; pcd, Boulonne-su-Mér; nl, Bonen; la, Gesoriacum or ''Bononia''), often called just Boulogne (, ), is a coastal city in Northern France. It is a sub-prefecture of the department of Pas-de-Calais. Boulogne lies on the ...
. Before being fitted with
canal
Canals or artificial waterways are waterways or engineered channels built for drainage management (e.g. flood control and irrigation) or for conveyancing water transport vehicles (e.g. water taxi). They carry free, calm surface flow un ...
s and
locks
Lock(s) may refer to:
Common meanings
*Lock and key, a mechanical device used to secure items of importance
*Lock (water navigation), a device for boats to transit between different levels of water, as in a canal
Arts and entertainment
* ''Lock ...
, the Liane
estuary
An estuary is a partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea. Estuaries form a transition zone between river environments and maritime environment ...
contributed directly to the ''fleuve marin côtier'' which abuts the Picardy estuaries up to the location of the two capes. It has been proposed in one variation of the project that its estuary, although significantly transformed by technology, should be part of a putative natural park, the ''Parc naturel marin à l'ouvert des estuaires picards et en mer d'Opale'', a proposal in preparation since 2008 and submitted to
public enquiry
A tribunal of inquiry is an official review of events or actions ordered by a government body. In many common law countries, such as the United Kingdom, Ireland, Australia and Canada, such a public inquiry differs from a royal commission in that ...
in 2011.
Morphology and tributaries
The average gradient of the Liane is 2.8 ‰. Its tributaries include the following:
Hydrology
The Liane is a very fast flowing river, but quite irregular. Its flow rate has been measured over a 27-year period (1965–1991), at
Hesdigneul-lès-Boulogne
Hesdigneul-lès-Boulogne (, literally ''Hesdigneul near Boulogne''; pcd, Hédignu-lès-Boulonne) is a commune in the Pas-de-Calais department in the Hauts-de-France region of France.
Geography
A forestry and farming village situated some so ...
near
Boulogne-sur-Mer
Boulogne-sur-Mer (; pcd, Boulonne-su-Mér; nl, Bonen; la, Gesoriacum or ''Bononia''), often called just Boulogne (, ), is a coastal city in Northern France. It is a sub-prefecture of the department of Pas-de-Calais. Boulogne lies on the ...
, a short way from its
mouth
In animal anatomy, the mouth, also known as the oral cavity, or in Latin cavum oris, is the opening through which many animals take in food and issue vocal sounds. It is also the cavity lying at the upper end of the alimentary canal, bounded on ...
. The watershed of the river at that point is 196 km², or approximately 80% of its maximum value of 244 km²).
The mean interannual flow rate or
discharge of the Liane at Hesdigneul-lès-Boulogne is 2.99 m³/s.
Just like its neighbour, the
Wimereux
Wimereux (; vls, Wimeruwe) is a commune in the Pas-de-Calais department in the Hauts-de-France region of France.
Geography
Wimereux is a coastal town situated some north of Boulogne, at the junction of the D233 and the D940 roads, on the b ...
, but unlike most Pas-de-Calais waterways, the Liane exhibits highly marked seasonal fluctuations. High waters occur at the end of autumn and in winter, characterised by monthly mean flow rates between 3.06 and 5.33 m³/s, from November to March inclusive with a maximum in January. Low waters occur in summer, from June to September, with a decrease in monthly mean flow rate descending to 0.76 m³/s in August. However variations in flow rate are much more pronounced over short periods or from year to year.
At low water, the 3-year low instantaneous flow rate can drop to 0.066 m³/s in the case of a dry five-year period or 66 litres per second, which can be described as severe.
Flood
A flood is an overflow of water ( or rarely other fluids) that submerges land that is usually dry. In the sense of "flowing water", the word may also be applied to the inflow of the tide. Floods are an area of study of the discipline hydrol ...
s can be very significant considering the modest size of this small river and its watershed. The instantaneous maximal flowrate 2 (IMFR2) and IMFR5 metrics are 37 and 52 m³ respectively. The IMFR10, or flow rate calculated from the ten-year flood, is 61 m³/s, the IMFR20 is 70 m³/s and the IMFR50 was 82 m³/s.
The maximum instantaneous flow rate recorded at Hesdigneul-lès-Boulogne during the 2-year measurement period was 47.3 m³/s on 1 December 1979, while the maximum daily average flow rate was 41.6 m³/s on 6 February 1988. Comparing the first of these values to the scale of the IMFR numbers, it becomes clear that the 1979 flood was hardly a 5-year event, and thus floods of this size are to be expected very frequently.
The Liane is a very fast-flowing small river, fed heavily by the high rainfall in its watershed. The watershed runoff curve number is 483 mm annually, which is substantially larger than the average of France based on all its watersheds, as well as, for example, the average for the watershed of the neighbouring
Lys which measures 249 mm at Wervicq-Sud. The specific flow rate reaches 15.3 litres per second per square kilometre of watershed.
Ecological status
Other than near its
source
Source may refer to:
Research
* Historical document
* Historical source
* Source (intelligence) or sub source, typically a confidential provider of non open-source intelligence
* Source (journalism), a person, publication, publishing institute o ...
, the Liane's water quality was mediocre to highly
polluted
Pollution is the introduction of contaminants into the natural environment that cause adverse change. Pollution can take the form of any substance (solid, liquid, or gas) or energy (such as radioactivity, heat, sound, or light). Pollutants, the ...
during the years 1980–1990, mainly as a result of
industrial
Industrial may refer to:
Industry
* Industrial archaeology, the study of the history of the industry
* Industrial engineering, engineering dealing with the optimization of complex industrial processes or systems
* Industrial city, a city dominate ...
and
urban waste
Municipal solid waste (MSW), commonly known as trash or garbage in the United States and rubbish in Britain, is a waste type consisting of everyday items that are discarded by the public. "Garbage" can also refer specifically to food waste, ...
. Towns and industries are now polluting less, but ploughing has conquered land from farming and pasture which have been pushed back in this region, and farmland erosion and fields which are kept barren in winter and autumn are a cause of the Liane's almost constant turbidity. In 2005, the Liane remained turbid and its French water quality grade ''insatisfaisante'' (unsatisfactory), with too much nitrates and organic substances from Carly onwards, according to the water agency. At the mouth at Boulogne, the Liane's waters are graded as ''mauvaise'' (bad), with all the indicators being bad: macro-pollutants, organic and oxidizable substances, azot substances (nitrates) and phosphoric substances.
The situation may be improved by the
Water Framework Directive
The Water Framework Directive 2000/60/EC is an EU directive which commits European Union member states to achieve good qualitative and quantitative status of all water bodies (including marine waters up to one nautical mile from shore) by 2015. ...
, and by the local ''Schéma d'Aménagement et de Gestion des Eaux'' water management scheme.
For some years a
fishermen
A fisher or fisherman is someone who captures fish and other animals from a body of water, or gathers shellfish.
Worldwide, there are about 38 million commercial and subsistence fishers and fish farmers. Fishers may be professional or recreat ...
's association has, through various activities, attempted to make the Liane known other than for its reputation as being highly polluted; while this is true around Boulogne-sur-Mer, there are some places where the Liane is a picturesque river with swarms of fish. The ''Association des Pêcheurs de la Vallée de la Liane'' fishermen's association even regularly deposits wild
trout
Trout are species of freshwater fish belonging to the genera '' Oncorhynchus'', ''Salmo'' and ''Salvelinus'', all of the subfamily Salmoninae of the family Salmonidae. The word ''trout'' is also used as part of the name of some non-salmoni ...
(known as "farios") to repopulate the river and replace the fish which they have caught.
See also
*
List of rivers of France
This is a list of rivers that are at least partially in France. The rivers are grouped by sea or ocean. The rivers flowing into the sea are sorted along the coast. Rivers flowing into other rivers are listed by the rivers they flow into. Some rive ...
Notes
References
External links
Société de Pêche de DesvresBanque Hydro – Station E5310210 la Liane à Hesdigneul-lès-Boulogne(do not tick the box "Station en service")
Altlas of floodable zonesof the Liane (downloadable)
{{Authority control
Rivers of the Pas-de-Calais
Rivers of France
Rivers of Hauts-de-France
0Liane